Gas-filled high-tension rectifier



Patented Jan. 2, 1945 GAS-FILLED HIGH-TENSION RECTIFIER Walther Miiller, Hamburg-Fuhlsbuttel, Germany No Drawing. Application January 22, 1943, Se-

rial No. 473,235. In Germany September 23,

1 Claim.

In addition to mercury vapour fillings, it is known to use rare gas fillings for high-voltage rectifiers. However, only the mercury vapour filled rectifiers have acquired practical importance,'because it has been found that rare gases are absorbed by the walls of the rectifier within a short time. Those gas-filled rectifiers that are known, such as the argon-filled rectifier, are not adapted to high-voltage use, because the pressure of the gas filling is of the order of magnitude of several ms. of mercury. In these rectifiers the absorption of gas by the rectifier walls is not of significant importance because the pressure is initially so high that even when part of the gas filling disappears the residual pressure remains sufliciently high for satisfactory operation.

In high-tension rectifiers the pressure of the gas filling can be only 0.1 to 0.8 10 mm. of mercury. Any absorption of the gas is therefore of significant importance and for example, it is found that an argon filling of 0.8 lmm. of mercury is absorbed in a few hours.

On the other hand, the use of rare gas fillings instead of mercury vapour fillings offers the great advantage that the operating temperature limitations existin in the case of the mercuryvapour filled rectifier disappear. It has been found that it is possible to use a high-tension rectifier with a gas filling, if use is made of a filling of xenon with a small addition of mercury vapour. Such a filling, in contradistinction to fillings of the other rare gases and mixtures of rare gas and mercury vapour previously used, is consumed by the discharge to such a small extent that a satisfactory life is obtained for the hightension rectifier. An explanation of the difierent behaviour of the said mixture is as follows:

The disappearance of the gas filling is partly brought about by the action of the ions which originate at the time of current passage through the rectifier. These ions continue to exist during the blocking time of the rectifier and are flung into the walls by the oppositely directed field existing in the rectifier during the blocking time.

When use is made of a mixture of-xenon and mercury vapour, the low ionisation voltage of the mercury results in substantially mercury ions being produced and the xenon atoms remain comparatively unaffected. The mercury atoms which are flung into the walls may be easily replaced from a small drop of mercury lying on the bottom of the rectifier. During the time or" current passage through the rectifier a certain percentage of the xenon atoms are brought to a meta-stable level whose energy amounts to 8.28 to 9.40 electron volts. During the blocking time these long living, meta-stable xenon atoms are not capable of ionising'mercury atoms which have the ionisation voltage 10.85 electron volts. This is because of the particular place which xenon occupies in the series of the other rare gases, the meta-stable conditions of which have a higher energy than the ionisation work of mercury (for example helium 20.86 to 21.12 volts, argon 11.56 to 11.77 volts).

In contradistinction to the xenon filling, an argon filling would produce a certain number of mercury ions durin the blocking time of the rectifier and these mercury ions in turn produce argon ions by impact, which ions are caught by the field and neutralized on the walls.

What I claim is:

A high-tension electric discharge rectifier tube comprising a container and a gaseous filling consisting of Xenon and mercury vapor, the xenon being present in an amount equivalent to a pressure of 0.1 to 0.8 10- millimeters of mercury 

